Described herein are cobalt compounds, processes for making cobalt compounds, and compositions comprising cobalt compounds for use in deposition of cobalt-containing films.
Cobalt-containing films are widely used in semiconductor or electronics applications. Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) have been applied as the main deposition techniques for producing thin films for semiconductor devices. These methods enable the achievement of conformal films (metal, metal oxide, metal nitride, metal silicide, etc.) through chemical reactions of metal-containing compounds (precursors). The chemical reactions occur on surfaces which may include metals, metal oxides, metal nitrides, metal silicides, and other surfaces.
Films of transition metals, particularly manganese, iron, cobalt, and ruthenium, are important for a variety of semiconductor or electronics applications. For example, cobalt thin films are of interest due to their high magnetic permittivity. Cobalt-containing thin films have been used as Cu/low-k barriers, passivation layers, and capping layers for ultra-large scale integrated devices. Cobalt is under consideration for replacement of copper in wiring and interconnects of integrated circuits.
Some Co film deposition precursors have been studied in the art.
US 2016/0115588 A1 discloses cobalt-containing film forming compositions and their use in film deposition.
WO 2015/127092 A1 describes precursors for vapor deposition of cobalt on substrates, such as in ALD and CVD processes for forming interconnects, capping structures, and bulk cobalt conductors, in the manufacture of integrated circuitry and thin film products.
US 2015/0093890 A1 discloses metal precursors and methods comprising decomposing a metal precursor on an integrated circuit device and forming a metal from the metal precursor. The metal precursors are selected from the group consisting of (alkyne) dicobalt hexacarbonyl compounds substituted with straight or branched monovalent hydrocarbon groups having one to six carbon atoms, mononuclear cobalt carbonyl nitrosyls, cobalt carbonyls bonded to one of a boron, indium, germanium and tin moiety, cobalt carbonyls bonded to a mononuclear or binuclear allyl, and cobalt compound comprising nitrogen-based supporting ligands.
WO 2014/118748 A1 describes cobalt compounds, the synthesis of said cobalt compounds, and the use of cobalt compounds in the deposition of cobalt-containing films.
Keunwoo Lee et al. (Japanese Journal of Applied Physics, 2008, Vol. 47, No. 7, 5396-5399) describes deposition of cobalt films by metal organic chemical vapor deposition (MOCVD) using tert-butylacetylene (dicobalt hexacarbonyl) (CCTBA) as cobalt precursor and H2 reactant gas. The carbon and oxygen impurities in the film decrease with increased H2 partial pressure but the lowest amount of amount of carbon in the film was 2.8 at. % at 150° C. Increasing deposition temperature resulted in high impurity contents and a high film resistivity attributed to excessive thermal decomposition of the CCTBA precursor.
C. Georgi et al. (J. Mater. Chem. C, 2014, 2, 4676-4682) teaches forming Co metal films from (alkyne) dicobalt hexacarbonyl precursors. However, those precursors are undesirable because the films still contain high levels of carbon and/or oxygen resulting in high resistivity. There is also no proof in the literature to support the ability to deposit continuous thin films of Co.
JP2015224227 describes a general synthetic process for producing (alkyne) dicobalt hexacarbonyl compounds. (Tert-butyl methyl acetylene) dicobalt hexacarbonyl (CCTMA) is used to generate cobalt films with low resistivity. However, no improvement in film properties relative to (tert-butylacetylene)dicobalt hexacarbonyl (CCTBA) was demonstrated. In addition, (tert-butyl methyl acetylene) dicobalt hexacarbonyl is a high melting (ca. 160° C.) solid. Precursors which are liquid at <=100° C., or, more preferably, <=30° C., are more desirable.
Generally, limited options exist for ALD and CVD precursors that deliver high purity cobalt films or exhibit high selectivity for deposition of cobalt films on one substrate vs. other substrates. To enhance film uniformity, film continuity, electrical properties of the deposited films, and film deposition selectivity, the development of novel precursors is necessary and is needed for thin, high-purity cobalt films and bulk cobalt conductors